A rangefinder inspection scope is really a camera fitted having a rangefinder: a range-finding focusing mechanism allowing the photographer to measure the subject distance and take photographs that are in sharp focus. Most varieties of rangefinder show two images of the same subject, one of which moves whenever a calibrated wheel is turned; once the two images coincide and fuse into one, the length can be read from the wheel. Older, non-coupled rangefinder cameras display the focusing distance and require the photographer to transfer the worthiness to the lens focus ring; inspection scopes without built-in rangefinders could have an external rangefinder fitted into the accessory shoe. Earlier cameras of this type had separate viewfinder and rangefinder windows; later the rangefinder was integrated into the viewfinder. More contemporary designs have rangefinders coupled towards the focusing mechanism, so the lens is focused correctly once the rangefinder images fuse; compare with the focusing screen in non-autofocus SLRs.

Almost all digital cameras, and many later film cameras, measure distance using electroacoustic or electronic means and focus automatically (autofocus); however, it is not customary to talk of this functionality as a rangefinder.
History

The very first rangefinders, sometimes called "telemeters", appeared within the nineteenth century; the first rangefinder camera to become marketed was the 3A Kodak Autographic Special of 1916; the rangefinder was coupled.

Not itself a rangefinder inspection scope, the Leica I of 1925 had popularized using accessory rangefinders. The Leica II and Zeiss Contax I, both of 1932, were great successes as 35mm rangefinder cameras, during the Leica Standard, also introduced in 1932, the rangefinder was omitted. The Contax II (1936) integrated the rangefinder in the center of the viewfinder.
1957C60 Kodak Retina IIIC

Rangefinder cameras were common in the 1930s to the 1970s, however the more complex models lost ground to single-lens reflex (SLR) cameras.

Rangefinder cameras have been produced in every size and all sorts of film formats through the years, from 35mm through medium format (rollfilm) to large-format press cameras. Before the mid-1950s most were generally fitted to more costly models of cameras. Folding bellows rollfilm cameras, like the Balda Super Baldax or Mess Baldix, the Kodak Retina II, IIa, IIc, IIIc, and IIIC cameras and the Hans Porst Hapo 66e (a less expensive version of the Balda Mess Baldix), were often fitted with rangefinders.
Leica M7 rangefinder

The best-known rangefinder cameras take 35mm film, use focal plane shutters, and also have interchangeable lenses. These are Leica screwmount (also called M39) cameras produced for lens manufacturer Ernst Leitz Wetzlar by Oskar Barnack (which gave rise to very many imitations and derivatives), Contax cameras manufactured for Carl Zeiss Optics by inspection scope subsidiary Zeiss-Ikon and, after Germany's defeat in The second world war, produced again and then developed as the Ukrainian Kiev), Nikon S-series cameras from 1951C62 (with design inspired through the Contax and performance by the Leica), and Leica M-series cameras.
Contax II
Nikon SP and S3 cameras

The Nikon rangefinder cameras were "discovered" in 1950 by Life magazine photographer David Douglas Duncan, who covered the Korean War.[1] Canon manufactured several models in the 1930s before the 1960s; models from 1946 onwards were more or less compatible with the Leica thread mount. (From late 1951 these were completely compatible; the 7 and 7s were built with a bayonet mount for that 50 mm f/0.95 lens in addition to the thread mount for other lenses.)

Launched in 1940, The Kodak 35 Rangefinder was the very first 35 mm inspection scope produced by the Eastman Kodak Company. Other such cameras include the Casca (Steinheil, West Germany, 1948), Detrola 400 (USA, 1940C41), Ektra (Kodak, USA, 1941C8), Foca (OPL, France, 1947C63), Foton (Bell & Howell, USA, 1948), Opema II (Meopta, Czechoslovakia, 1955C60), Perfex (USA, 1938C49), Robot Royal (Robot-Berning, West Germany, 1955C76), and Witness (Ilford, Britain, 1953). Among the longer lasting marques, all but the Leica M succumbed available on the market to pressure from SLRs. The newest in the M-series are the M7, the first from the series to feature automatic exposure as well as an electronic shutter; and also the all-mechanical MP, an updated M6 with an M3-style rewind knob; and the new M8, Leica's first digital rangefinder.

In the usa the dependable and cheap Argus (especially the ubiquitous C-3 "Brick") was far and away the most popular 35mm rangefinder, with millions sold.

Interchangeable-lens rangefinder cameras with focal-plane shutters are greatly outnumbered by fixed-lens leaf-shutter rangefinder cameras. Typically the most popular design in the '50s were folding designs such as the Kodak Retina and also the Zeiss Contessa.

Within the 1960s many fixed-lens 35mm rangefinder cameras for the amateur market were produced by several manufacturers, mainly Japanese, including Canon, Fujica, Konica, Mamiya, Minolta, Olympus, Ricoh, and Yashica. Distributors for example Vivitar and Revue often sold rebranded versions of these cameras. While designed to be compact such as the Leica, they were a smaller amount expensive. Many of them, such as the Minolta 7sII and also the Vivitar 35ES, were fitted with high-speed, higher than normal quality optics. Though eventually replaced on the market with newer compact autofocus cameras, many of these older rangefinders still operate, having outlived the majority of their newer (and fewer well-constructed) successors.

Beginning with a inspection scope produced by the small Japanese company Yasuhara in the 1990s, there's been something of the revival of rangefinder cameras. Aside from the Leica M series, rangefinder models from this period include the Konica Hexar RF, Cosina, who helps make the Voigtl?nder Bessa T/R/R2/R3/R4 (the last three are made in both manual or aperture automatic version, which use respectly the "m" or "a" sign in model), and the Hasselblad Xpan/Xpan 2. Zeiss has a new model known as the Zeiss Ikon, also produced by Cosina, while Nikon has additionally produced expensive limited editions of their S3 and SP rangefinders to fulfill the demands of collectors and aficionados. General Tool inspection scope camera from the former Ussr the Zorki and FED, in line with the screwmount Leica, and also the Kiev are all around within the used market.